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Multiple Choice
Which of the following pairs of compounds are constitutional isomers?
A
Butane and 2-methylpropane
B
Cyclohexane and benzene
C
Ethane and ethene
D
Methanol and ethanol
Verified step by step guidance
1
Understand the definition of constitutional isomers: Constitutional isomers are compounds that have the same molecular formula but different connectivity of atoms within the molecules.
Analyze the molecular formula of each pair of compounds: For example, butane (C₄H₁₀) and 2-methylpropane (C₄H₁₀) have the same molecular formula.
Check the connectivity of atoms: Compare the structure of butane, which is a straight chain, with 2-methylpropane, which has a branched chain. This difference in connectivity confirms they are constitutional isomers.
Repeat the analysis for the other pairs: Cyclohexane (C₆H₁₂) and benzene (C₆H₆) have different molecular formulas, so they cannot be constitutional isomers. Ethane (C₂H₆) and ethene (C₂H₄) also have different molecular formulas. Methanol (CH₄O) and ethanol (C₂H₆O) have different molecular formulas as well.
Conclude that only butane and 2-methylpropane are constitutional isomers, as they share the same molecular formula but differ in the connectivity of their atoms.